do_sys_name_to_handle(): use kzalloc() to fix kernel-infoleak

syzbot identified a kernel information leak vulnerability in
do_sys_name_to_handle() and issued the following report [1].

[1]
"BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x100 lib/usercopy.c:40
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
_copy_to_user+0xbc/0x100 lib/usercopy.c:40
copy_to_user include/linux/uaccess.h:191 [inline]
do_sys_name_to_handle fs/fhandle.c:73 [inline]
__do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
__se_sys_name_to_handle_at+0x949/0xb10 fs/fhandle.c:94
__x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
...

Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
__kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0x121/0x3c0 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
do_sys_name_to_handle fs/fhandle.c:39 [inline]
__do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
__se_sys_name_to_handle_at+0x441/0xb10 fs/fhandle.c:94
__x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
...

Bytes 18-19 of 20 are uninitialized
Memory access of size 20 starts at ffff888128a46380
Data copied to user address 0000000020000240"

Per Chuck Lever's suggestion, use kzalloc() instead of kmalloc() to
solve the problem.

Fixes: 990d6c2d7aee ("vfs: Add name to file handle conversion support")
Suggested-by: Chuck Lever III <chuck.lever@oracle.com>
Reported-and-tested-by: <syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com>
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Link: https://lore.kernel.org/r/20240119153906.4367-1-n.zhandarovich@fintech.ru
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

exportfs: add helpers to check if filesystem can encode/decode file handles

The logic of whether filesystem can encode/decode file handles is open
coded in many places.

In preparation to changing the logic, move the open coded logic into
inline helpers.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231023180801.2953446-2-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

fsnotify: move fsnotify_open() hook into do_dentry_open()

fsnotify_open() hook is called only from high level system calls
context and not called for the very many helpers to open files.

This may makes sense for many of the special file open cases, but it is
inconsistent with fsnotify_close() hook that is called for every last
fput() of on a file object with FMODE_OPENED.

As a result, it is possible to observe ACCESS, MODIFY and CLOSE events
without ever observing an OPEN event.

Fix this inconsistency by replacing all the fsnotify_open() hooks with
a single hook inside do_dentry_open().

If there are special cases that would like to opt-out of the possible
overhead of fsnotify() call in fsnotify_open(), they would probably also
want to avoid the overhead of fsnotify() call in the rest of the fsnotify
hooks, so they should be opening that file with the __FMODE_NONOTIFY flag.

However, in the majority of those cases, the s_fsnotify_connectors
optimization in fsnotify_parent() would be sufficient to avoid the
overhead of fsnotify() call anyway.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230611122429.1499617-1-amir73il@gmail.com>

exportfs: check for error return value from exportfs_encode_*()

The exportfs_encode_*() helpers call the filesystem ->encode_fh()
method which returns a signed int.

All the in-tree implementations of ->encode_fh() return a positive
integer and FILEID_INVALID (255) for error.

Fortify the callers for possible future ->encode_fh() implementation
that will return a negative error value.

name_to_handle_at() would propagate the returned error to the users
if filesystem ->encode_fh() method returns an error.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/linux-fsdevel/ca02955f-1877-4fde-b453-3c1d22794740@kili.mountain/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230524154825.881414-1-amir73il@gmail.com>

exportfs: allow exporting non-decodeable file handles to userspace

Some userspace programs use st_ino as a unique object identifier, even
though inode numbers may be recycable.

This issue has been addressed for NFS export long ago using the exportfs
file handle API and the unique file handle identifiers are also exported
to userspace via name_to_handle_at(2).

fanotify also uses file handles to identify objects in events, but only
for filesystems that support NFS export.

Relax the requirement for NFS export support and allow more filesystems
to export a unique object identifier via name_to_handle_at(2) with the
flag AT_HANDLE_FID.

A file handle requested with the AT_HANDLE_FID flag, may or may not be
usable as an argument to open_by_handle_at(2).

To allow filesystems to opt-in to supporting AT_HANDLE_FID, a struct
export_operations is required, but even an empty struct is sufficient
for encoding FIDs.

Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230502124817.3070545-4-amir73il@gmail.com>

do_sys_name_to_handle(): constify path

Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

switch file_open_root() to struct path

... and provide file_open_root_mnt(), using the root of given mount.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs: delete repeated words in comments

Delete duplicate words in fs/*.c.
The doubled words that are being dropped are:
that, be, the, in, and, for

Link: https://lkml.kernel.org/r/20201224052810.25315-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/handle.c - fix up kerneldoc

When building with W=1, we get some kerneldoc warnings:

CC fs/fhandle.o
fs/fhandle.c:259: warning: Function parameter or member 'flags' not described in 'sys_open_by_handle_at'
fs/fhandle.c:259: warning: Excess function parameter 'flag' description in 'sys_open_by_handle_at'

Fix the typo that caused it.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs: Copy struct mount.mnt_id to userspace using put_user()

The mnt_id field can be copied with put_user(), so there is no need to
use copy_to_user(). In both cases, hardened usercopy is being bypassed
since the size is constant, and not open to runtime manipulation.

This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.

Signed-off-by: David Windsor <dave@nullcore.net>
[kees: adjust commit log]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

do_handle_open() should be static

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fhandle: move compat syscalls from compat.c

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Replace <asm/uaccess.h> with <linux/uaccess.h> globally

This was entirely automated, using the script by Al:

PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>'
sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \
$(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.

Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/coredump: prevent fsuid=0 dumps into user-controlled directories

This commit fixes the following security hole affecting systems where
all of the following conditions are fulfilled:

- The fs.suid_dumpable sysctl is set to 2.
- The kernel.core_pattern sysctl's value starts with "/". (Systems
where kernel.core_pattern starts with "|/" are not affected.)
- Unprivileged user namespace creation is permitted. (This is
true on Linux >=3.8, but some distributions disallow it by
default using a distro patch.)

Under these conditions, if a program executes under secure exec rules,
causing it to run with the SUID_DUMP_ROOT flag, then unshares its user
namespace, changes its root directory and crashes, the coredump will be
written using fsuid=0 and a path derived from kernel.core_pattern - but
this path is interpreted relative to the root directory of the process,
allowing the attacker to control where a coredump will be written with
root privileges.

To fix the security issue, always interpret core_pattern for dumps that
are written under SUID_DUMP_ROOT relative to the root directory of init.

Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

vfs: read file_handle only once in handle_to_path

We used to read file_handle twice. Once to get the amount of extra
bytes, and once to fetch the entire structure.

This may be problematic since we do size verifications only after the
first read, so if the number of extra bytes changes in userspace between
the first and second calls, we'll have an incoherent view of
file_handle.

Instead, read the constant size once, and copy that over to the final
structure without having to re-read it again.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix misspellings of "whether" in comments.

"Whether" is misspelled in various comments across the tree; this
fixes them. No code changes.

Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

exportfs: add FILEID_INVALID to indicate invalid fid_type

This commit adds FILEID_INVALID = 0xff in fid_type to
indicate invalid fid_type

It avoids using magic number 255

Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Vivek Trivedi <vtrivedi018@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

switch simple cases of fget_light to fdget

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs: prefer ->dentry->d_sb to ->mnt->mnt_sb

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs: mnt_id/mnt_group_id moved

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fhandle.c: add <linux/personality.h> for ia64

force_o_largefile() on ia64 is defined in <asm/fcntl.h> and requires
<linux/personality.h>.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

vfs: Add open by file handle support

[AV: duplicate of open() guts removed; file_open_root() used instead]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs: Add name to file handle conversion support

The syscall also return mount id which can be used
to lookup file system specific information such as uuid
in /proc/<pid>/mountinfo

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>